Process of covering perforated rolls



April 26, 1938. c. c. THACKRAY 2,115,543

PROCESS OF COVERING PERFORATED ROLLS Filed Oct. 17, 1956 IN VENTOR.

ATTORNEY.

Wm C'ozam Patented Apr. 26, 1938 UNITE PROCESS OF CQVERING PERFORATEDROLLS Garden Cousens Thackray, Westmount, Quebec,

Canada, assignor to United States Rubber Products, Inc, New York, N. Y.,a corporation of Delaware Application October 1'7, 1936, Serial No.106,255

@laims.

This invention relates to a process of covering perforated rolls, moreparticularly to a process for forming perforated coverings ofrubber-like material on perforated hollow rolls. The present in- 1vention, while applicable generally to the forming of perforated rubbercoverings on perforated rolls, relates more particularly to the formingof such coverings on the perforated rolls used in the paper makingindustry, such as suction press and couch 'rolls.

Perforated metal suction rolls have been used in the paper industry fora long time, and more recently there have been applied to these rolls Aperforated rubber coverings. However, considerable difficulty has beenhad in properly forming the perforations and in properly adhering thecovering to the metal body of the roll. One method of application hasbeen to apply a rubber covering to the perforated metal roll, vulcanizethe covering, and then drill holes from the outside through the rubbercovering in registry with the perforations in the metal roll. However,the rolls in many cases are very long and the perforations arerelatively small and closely spaced, and it has therefore been verydiflicult in drilling from the outside to obtain proper registry of thedrilled holes in the rubber covering with the perforations in the metalroll. As a result, it was customary to make the drilled holes in thecovering somewhat smaller than those in the roll body to insure that thedrilled hole in the covering would be entirely within the circumferenceof the corresponding perforation in the roll. This cutting down the sizeof the hole in the rubber covering necessarily limits the flow of waterinto the roll from the paper web being operated upon, and in additionthe drilled hole in the rubber has not the desired smoothness.

To obviate the above objection, another procedure was devised in whichthe rubber covering was. applied to the outer surface of the perforatedmetal roll, then tightly wrapped with cloth to retain the rubber inplace during vulcaniza- 45 tion, after which pins were driven throughthe perforations of the roll from the inside outwardly and entirelythrough the rubber covering and retaining layer of fabric. The roll wasthen vulcanized, the fabric covering removed, and the pins driven backinwardly and removed from the interior of the roll. This procedure isdisclosed in patent of Wellsford No. 1,988,640, and is an improvementover the prior process in that the holes in the rubber covering areexactly in registry with the holes .in the metal roll and also the wallsof the holes in the rubber have a smooth molded surface.

However, there has been serious difficulty in securing good adhesion ofthe rubber to the metal, because when the pins are driven outwardlythrough the holes in the metal roll, they tend to lift away both therubber covering and its confining fabric wrapping, and as a result, airpockets are formed between the roll and its rubber cover around each ofthe pins. When the covering is vulcanized and the roll put in use, thecovering then tends to separate.

An object of the present invention is to provide an improved process forforming a perforated covering of rubber-like material on perforatedrolls.

Another object is to provide an improved union between the rubbercovering and the metal roll.

For a detailed disclosure of the nature and objects of the inventionreference is had to the accompanying specification and drawing, in whichlatter:

Figure 1 is a more or less diagrammatic sectional view of a Vulcanizerand roll, and

Figure 2 is a detail enlarged section through the roll at anintermediate stage in the process.

The process will be described in connection with the appended drawing,and in carrying out the invention in one embodiment a roll designatedgenerally by the numeral I, such as a suction press roll, has a metalshell 2 provided with numerous small perforations 3. Over this shell isdisposed the covering 4 of suitable material, such as unvulcanizedrubber. This rubber may be compounded in any suitable way to impart thedesired properties to the covering when in use, and usually is appliedby rolling around the roll a suitable number of layers of sheet stockuntil the desired thickness has been obtained. In applying the sheetrubber stock to the roll, any of the usual expedients for obtaining goodadhesion may be employed. A strong wrapping of suitable confiningmaterial, such as fabric strip 5, is then wrapped around the rubbercovering so as to firmly bind it to the roll during vulcanization.

Pins 6 are then driven through the perforations 3 of the roll from theinside outwardly and entirely through the rubber covering 4 and fabricwrapping 5. These pins are tapered at their outer ends as shown at 1.Due to the pressure exerted when the pins 5 are driven through therubber layer 4 and fabric 5, and also to the frictional resistance ofthe rubber and fabric, these are forced upwardly in a more or lessconical shape around the exposed end of each pin, as shown at r 8. Thisresults in the formation of small air pockets 9 disposed around each pinat the point where it projects outside of the roll body 2. As beforepointed out, if the roll were vulcanized in this condition, these airpockets 9 would remain and would prevent proper adhesion of the rubbercovering to the roll. By the present invention the roll, in thecondition shown in Fig. 2, is sealed at each end as by the caps l0 andis then placed in a vulcanizer I l. A pipe l2 communicates at one endwith the outer atmosphere, and at its other end is connected through aswivel joint l3 with the interior of the roll. The roll is rotatablymounted in the vulcanizer in any suitable manner (not shown) for apurpose to be later described.

Steam and air pressure are then applied in the vulcanizer to theexterior of the roll, the steam pressure being gradually raised until apressure sufficient to give the desired vulcanizing temperature isattained. As the rubber covering is initially heated up, and beforevulcanization has set it, it becomes softened and plastic, and by reasonof the external steam and air pressure, the covering is forced downfirmly into union with the metal roll at all points. Since the pins 6have only a slide fit in the perforations 3, the air in the pockets 9can escape around the pins into the interior of the roll and thence byway of the pipe 12 to the outer air. After this partial differentialcure or vulcanization has proceeded to the desired extent, the pipe l2and cap III are removed so as to permit free access to the interior ofthe roll. The vulcanizer is then again closed and steam and air pressureagain applied, the steam pressure being gradually raised to the desiredvulcanizing pressure, and since the interior of the roll is now open,the pressure will be the same on the interior and exterior of the roll.

The times of vulcanization will, of course, be varied in a manner wellknown to those skilled in the art according to the size of the roll,thickness of the cover, composition of the rubber stock, and plastometerreading required by the customer.

' Rotation of the roll during the vulcanizing periods is necessary inorder to prevent water pockets forming inside the roll from condensedsteam.

Upon completion of the vulcanization the roll is removed from thevulcanizer, the outer fabric wrapping released, and the pins 6 drivenback into the interior of the roll. The surface of the rubber coveringmay then be ground to the size and finish desired for the purpose.

While the invention has been specifically described in connection withthe use of rubber as the covering material, it is obvious that anysuitable rubber-like material having the desired properties may beemployed, such as synthetic rubbers or imitation rubbers, orpolychlorobutadiene, commonly known as Duprene.

It will be seen that by the invention, a perforated rubber cover for aperforated roll can be formed in such a manner that the holes in therubber and metal are in exact registry, the walls of the holes in therubber are smoothly molded, and at the same time strong adhesion hasbeen secured between the rubber cover and metal body throughout theunperforated area of the roll.

It is obvious that modifications may be made in the process and it isnot desired to limit it otherwise than as set forth in the appendedclaims.

Having thus described my invention, what I claim and desire to protectby Letters Patent is:

1. A method of forming perforated coverings of rubber-like material onperforated hollow rolls which comprises applying a covering of saidmaterial in at least a partially plastic condition to a perforated roll,enclosing the covering with perforatable confining material, drivingpins from the interior of the roll through its perforations, thecovering material and the confining material, whereby the coveringmaterial is separated from the roll around said perforations, applyingheat and external pressure around the projecting portions of said pinsto produce complete union of the covering and roll at the separationsaround the roll perforations, setting the covering to an elastic,non-plastic condition, withdrawing said pins, and removing the confiningmaterial.

2. A method of forming perforated coverings of rubber-like material onperforated hollow rolls which comprises applying a covering of saidmaterial in at least a partially plastic condition to a perforated roll,enclosing the covering with perforatable confining material, drivingpins from the interior of the roll through its perforations, thecovering material and the confining material, whereby the coveringmaterial is separated from the roll around said perforations,temporarily softening the covering material while maintaining an excessof fluid pressure on the exterior of the assembly, to thereby reunitethe covering and the roll at the points of separation, setting thecovering to a non-plastic condition, withdrawing said pins, and removingthe confining material.

3. A method of forming perforated coverings of rubber-like material onperforated hollow rolls which comprises applying a covering of said ma.-terial in at least a partially plastic condition to a roll, wrapping thecovering with sheet confining material, driving pins from the rollinterior through its perforations, the covering material and theconfining material, whereby the covering material is separated from theroll around said perforations, softening and then partially setting thecovering material by heat while main taining an excess of fiuid pressureon the assembly exterior, to thereby reunite the covering and roll atthe points of separation, completely setting the covering to anon-plastic condition by heat, withdrawing said pins, and removing theconfining material.

4. A method of forming perforated rubber coverings on perforated hollowrolls which comprises applying a covering of plastic rubber to a roll,wrapping the covering with textile fabric, driving pins from the rollinterior through said perforations, whereby the covering material isseparated from the roll around said perforations, rubber covering andfabric, softening and inducing vulcanization of the covering by heatwhile maintaining an excess of fluid pressure on the roll exterior, tothereby reunite the covering and roll at the points of separation,completing the vulcanization under equalized exterior and interiorpressure, withdrawing said pins, and removing the fabric wrapping.

.5. A method of forming perforated rubber coverings on perforated hollowrolls which comprises applying a covering of unvulcanized rubber to aroll, wrapping the covering with textile fabric, driving pins throughsaid perforations, rubber covering and fabric, whereby the coveringmaterial is separated from the roll around said perforations, partiallyvulcanizing the covering in the presence of an excess of steam pressureon the roll exterior, to thereby reunite the covering and roll at thepoints of separation, completing the vulcanization under equalizedexterior and interior steam pressure on the roll, rotating the rollduring vulcanization, withdrawing said pins, and removing the fabricwrapping.

GARDEN COUSENS THACKRAY.

